In constructing multi-level buildings, it has been commonplace to load materials to be used in the construction of the multi-level building on a transport truck, or the like, or on a pallet which is then placed on the transport truck. The materials are then transported by truck, or the like, to the building site. Once at the building site, the material is unloaded from the truck and raised with a construction elevator or crane. A platform or some load carrying device protrudes from one or more of the floors of the multi-level building under active construction. The elevator or crane then hoists the material off the truck, or from the unloading site if the material has already been unloaded off the truck, to the unloading platform at the specific floor level in the multi-level building. The material is then moved off the platform and distributed and installed as required around the floor level under construction.
A problem with this traditional material handling system is that it is inefficient and prone to delays. For instance, transport trucks may not be readily available at the time that the materials are ready to be loaded onto the truck. At the construction site, the construction elevator or crane may be in active use for other things and not immediately available for unloading the material off the truck at the time the truck arrives at the construction site. Often the construction materials are heavy and it is not possible to readily unload the materials off the truck without the aid of a high powered mechanical device such as a construction elevator or a crane, which may not be immediately available. Dollies, jacks, and the like, can be used but they are not adaptable to all situations. As a result, since time is money in the construction of a building, expensive delays occur.
U.S. Pat. No. 4,907,935, Mankey, issued Mar. 13, 1990, discloses a cargo transporter having a cargo platform, mounted on a frame. The frame is supported by lift assemblies, which are mounted on wheel assemblies. Each lift assembly has a leg having an upper end which supports the frame and a lower end connected to the wheel assembly. Each lift assembly also has a support arm having an upper end pivotally connected to the frame and a lower end pivotally connected to the leg. Each lift assembly also has a hydraulic cylinder and piston rod, mounted between the leg and a bell crank of the support arm for changing the angle between the leg and the support arm, to cause the frame in the cargo platform to move vertically. A plurality of hydraulic cylinders and piston rods are mounted between the frame and the cargo platform for maneuvering the cargo platform relative to the frame.
U.S. Pat. No. 4,915,240, Konstant, issued Apr. 10, 1990, discloses a pallet rack comprising at least one pair of spaced, parallel rails and first and second wheeled carts mounted in rolling relation with the pair of rails, the wheels of first and second carts respectively rolling on the same rolling surfaces. The front wheels of the second cart are positioned between the front and rear wheels of the first cart. As the result of this, the second cart can roll between a first, vertically overlying position relative to the first cart, and a second position where most of the second cart is spaced along the rails from the first cart.
U.S. Pat. No. 4,982,851, Konstant, issued Jan. 8, 1991, discloses a pallet rack comprising at least one pair of spaced, parallel rails and at least one wheeled cart mounted in rolling relation with the pair of rails and defining a load-carrying area. By this invention a cross brace extends between the rails, being positioned to support the bottom of a weak or poorly placed pallet placed on the rails adjacent the front end. The cross brace defines a space adjacent each of the rails to permit the front end of the cart to roll to the front end of the rails between the cross brace and each rail. The cart comprises a pair of wheel-carrying side members positioned parallel to the rails, plus transverse support members connecting the side members. The transverse support members are spaced from the cart front end by a distance sufficient to allow the front end of the cart to roll between the cross brace and each rail.
U.S. Pat. No. 4,818,171, Burkholder, issued Apr. 4, 1989, discloses a pallet transferring arrangement and method for positioning a pallet transfer deck relative to a load transfer station. The pallet transferring arrangement has a jack assembly for elevationally moving a load carrying member between first and second spaced positions relative to a vehicle frame. First and second guide assemblies guide the load carrying member and a supporting arrangement movably supports a pallet transfer deck on the load carrying member for movement in a plane. A plurality of replaceable deck positioning socket members engage a plurality of replaceable deck positioning cone members at the second position of the load carrying member and maintains the pallet transfer deck from movement in the plane. The plurality of deck positioning socket members are free from engagement with the deck positioning cone members at the first position of the load carrying members. A ground engaging foot is connected to and movable with the second guide assembly, and supports the load carrying member at a first position. Thus, pallet transfer deck positioning and stability are achieved in an efficient and economical manner. The pallet transferring arrangement is particularly suited for use on automatic guided vehicles.